Methods for packaging a microelectromechanical systems device

ABSTRACT

A method for packaging a MEMS device includes the following steps. A metal cap is provided that is partially anchored to a wafer comprising the MEMS device where at least one point between the cap and the wafer is unanchored, the metal cap arranged to at least substantially extend over the MEMS device. An electrical contact pad is electrically coupled to the MEMS device. A sealing layer is provided over the metal cap and the wafer such that the sealing layer seals a gap between an unanchored portion of the metal cap and the wafer to encapsulate the MEMS device, where the electrical contact pad and the metal cap include the same composition.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of a U.S. application Ser. No.16/221,683, filed on 2018 Dec. 17, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

Various embodiments relate to microelectromechanical systems (MEMS)packages and methods for packaging a MEMS device.

2. Description of the Prior Art

Wafer level packaging (WLP) is a popular method for packaging MEMSdevices, as it allows the MEMS package to have a small form factor, andalso allows the processes of wafer fabrication, packaging, testing andburn-in to be conducted under one production floor. A commonly employedWLP technique is wafer level capping. Wafer level capping involvesbonding a cap wafer onto a device wafer. The resultant MEMS packagestypically have form factors in the range of 200 um to 250 um. MEMSmanufacturers are facing increased pressure to reduce the form factor ofMEMS packages to less than 200 um in thickness. Also, there is a need toshield the MEMS devices from electromagnetic (EM) interference,especially in view of the increasing density of circuits in electronicdevices. Currently there is no integrated WLP solution that canencapsulate MEMS devices while also providing EM shielding, unlessadditional processes are introduced to form a separate EM shield in theMEMS package.

SUMMARY OF THE INVENTION

According to various non-limiting embodiments, there may be provided aMEMS package including: a wafer having a MEMS device; a metal cappartially anchored to the wafer where at least one point between the capand the wafer is unanchored, the metal cap at least substantiallyextending over the MEMS device; an electrical contact pad electricallycoupled to the MEMS device; and a sealing layer disposed over the metalcap and the wafer, such that the sealing layer seals a gap between anunanchored portion of the metal cap and the wafer to encapsulate theMEMS device; wherein the electrical contact pad and the metal capinclude the same composition.

According to various non-limiting embodiments, there may be provided amethod for packaging a MEMS device. The method may include: providing ametal cap that is partially anchored to a wafer including the MEMSdevice where at least one point between the cap and the wafer isunanchored, the metal cap arranged to at least substantially extend overthe MEMS device; electrically coupling an electrical contact pad to theMEMS device; and providing a sealing layer over the metal cap and thewafer such that the sealing layer seals a gap between an unanchoredportion of the metal cap and the wafer to encapsulate the MEMS device;wherein the electrical contact pad and the metal cap include the samecomposition.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilyto scale, emphasis instead generally being placed upon illustrating theprinciples of the invention. In the following description, variousembodiments are described with reference to the following drawings, inwhich:

FIGS. 1-10 illustrate a method for packaging a MEMS device according tovarious non-limiting embodiments through a series of simplifiedcross-sectional views.

FIG. 11 illustrates a simplified cross-sectional view of a MEMS packageaccording to various non-limiting embodiments.

FIG. 12A illustrates a partial cross-sectional view of the MEMS packageof FIG. 11.

FIG. 12B illustrates a partial top view of a metal cap of a MEMS packageaccording to various non-limiting embodiments.

FIG. 13 illustrates a flow diagram of a method for packaging a MEMSdevice according to various non-limiting embodiments.

DETAILED DESCRIPTION

Embodiments described below in context of the MEMS packages areanalogously valid for the respective methods, and vice versa.Furthermore, it will be understood that the embodiments described belowmay be combined, for example, a part of one embodiment may be combinedwith a part of another embodiment.

It will be understood that any property described herein for a specificMEMS package may also hold for any MEMS package described herein. Itwill be understood that any property described herein for a specificmethod may also hold for any method described herein. Furthermore, itwill be understood that for any MEMS package or method described herein,not necessarily all the components or steps described must be enclosedin the device or method, but only some (but not all) components or stepsmay be enclosed.

It should be understood that the terms “on”, “over”, “top”, “bottom”,“down”, “side”, “back”, “left”, “right”, “front”, “lateral”, “side”,“up”, “down” etc., when used in the following description are used forconvenience and to aid understanding of relative positions ordirections, and not intended to limit the orientation of any device, orstructure or any part of any device or structure. In addition, thesingular terms “a”, “an”, and “the” include plural references unlesscontext clearly indicates otherwise. Similarly, the word “or” isintended to include “and” unless the context clearly indicatesotherwise.

The term “coupled” (or “connected”) herein may be understood aselectrically coupled or as mechanically coupled, for example attached orfixed, or just in contact without any fixation, and it will beunderstood that both direct coupling or indirect coupling (in otherwords: coupling without direct contact) may be provided.

According to various embodiments, a method for packaging a MEMS devicemay be a wafer-level packaging method that is able to provide the MEMSdevice with an integrated electromagnetic shield, while reducing thenumber of process steps. By using wafer-level packaging, instead ofother packaging methods like wafer cap packaging, the method may allowfor the MEMS package to be small in form factor, for example, less than150 um in thickness. The method may also add robustness to the MEMSpackage. The method may also allow for thin-film encapsulation to theMEMS device. The encapsulation may include a metal cap, which shieldsthe MEMS device from electromagnetic (EM) interference. The method mayinclude forming the metal cap and redistribution layer (RDL) in the sameprocess steps, such that no additional process steps are required toform the EM shield. The method may include forming a lateral releasevia, for releasing sacrificial material to form cavities in the MEMSdevice. The method may offer the advantages of a faster, cheaper, andsafer process of releasing sacrificial material to form cavities in theMEMS device. Also, using a lateral release via instead of a verticalrelease via may save space in the device footprint. Unlike a MEMSpackage with a vertical release via where the MEMS device cannot bepositioned directly underneath the vertical release via; by using alateral release via, the MEMS device need not be offset in positionrelative to the release via. The method may allow for only one mask thatis dedicated to the packaging process. In other words, only oneadditional mask as compared to a MEMS device fabrication process, forencapsulating the MEMS device may need to be used with the methoddescribed in more detail, below.

FIGS. 1-10 illustrate a method for packaging a MEMS device according tovarious non-limiting embodiments through a series of simplifiedcross-sectional views.

FIG. 1 illustrates a non-limiting process 100. The process 100 mayinclude providing a device wafer 140. The device wafer 140 may include aMEMS device 110 and a contact area 120. The portion of the device wafer140 that houses the MEMS device 110 may be referred herein as the devicearea. The contact area 120 may house electrical contact points 112 a,112 b for the MEMS device 110. The electrical contact points 112 a, 112b may be electrically coupled to the MEMS device 110. For example, theMEMS device 110 may include at least one electrode 108 a, 108 b, and theelectrical contact points 112 a, 112 b may be connected to the at leastone electrode 108 a, 108 b. In a non-limiting embodiment, there may bemore than two electrodes; although two electrodes are depicted inFIG. 1. The device wafer 140 may include a substrate 102 and an activeregion 104. The substrate 102 may include, for example, silicon orglass. The substrate 102 may also include integrated circuits, forexample, may be a CMOS device wafer. The active region 104 may bearranged over the substrate 102. The active region 104 may includeelectrodes 108 a, 108 b of the MEMS device 110. The upper electricalcontact point 112 a in the contact area 120 may be formed in the samelayer, and of the same material, as the upper electrode 108 a.Similarly, the lower electrical contact point 112 b in the contact area120 may be formed in the same layer, and of the same material, as thelower electrode 108 b. The electrodes 108 a, 108 b, and the electricalcontact points 112 a, 112 b may be formed from electrically conductivematerial, for example at least one of molybdenum (Mo), tungsten (W),aluminum (Al), platinum (Pt), other suitable metals, or combinationsthereof.

The active region 104 may include a moveable member, for example, aflexible membrane, that may convert electrical energy to kinetic energy.The moveable member may be for example, a piezoelectric transducer or acapacitive transducer. The active region 104 may include a piezoelectricmaterial, such as at least one of aluminum nitride (AlN), scandium-dopedAlN (ScAlN), lithium niobate (LiNbO₃), lithium tantalate (LiTa₂O₃), zincoxide (ZnO), lead zirconate titanate (PZT), polyvinylidene fluoride(PVDF), any other thin-film piezoelectric material, or combinationsthereof. The active region 104 may also, or alternatively, includesilicon. A lower sacrificial member 106 may be embedded in the substrate102 such that it comes into contact with the active region 104. Thelower sacrificial member 106 may define a space that will subsequentlyform a lower cavity underneath the active region 104 within the devicearea. The lower sacrificial member 106 may include, or may be formedfrom but is not limited to, any one of silicon dioxide (SiO₂), siliconnitride (SiN), tungsten (W), Molybdenum (Mo), aluminum nitride (AlN),aluminum oxide (Al₂O₃), or a combination of at least one of thesematerials. The device area may include a vertical via 114 that extendsfrom a top surface of the active region 104 to a bottom surface of theactive region 104 that is in contact with the substrate 102. The bottomsurface is opposite to the top surface. The vertical via 114 exposes thelower sacrificial member 106.

The process 100 may include etching the substrate 102 to form an areadefining a lower cavity of the MEMS device 110. The process 100 mayfurther include depositing a first sacrificial material 130 into thearea to form the lower sacrificial member 106. The process 100 mayoptionally include depositing a seed layer over the substrate 102. Theprocess 100 may include depositing a bottom metal layer, and thenpatterning the bottom metal layer to form the lower electrode 108 b andthe lower electrical contact point 112 b. The process 100 may includedepositing an active material, such as a piezoelectric material orsilicon, over the bottom metal layer to form the moveable member. Theprocess 100 may include depositing a top metal layer, and thenpatterning the top metal layer to form the upper electrode 108 a and theupper electrical contact point 112 a. The process 100 may furtherinclude depositing more of the active material over the top metal layer,and then etching the active material to reach the lower sacrificialmember 106, thereby forming the vertical via 114.

FIG. 2 illustrates a non-limiting process 200. The process 200 mayinclude depositing a layer of second sacrificial material 230 over thedevice wafer 140. The second sacrificial material 230 may be identicalin composition as the first sacrificial material 130, or may consist ofany other material that can be released together with the lowersacrificial member 106 using the same etching solution. The secondsacrificial material 230 may include, or may be, a dielectric materialin a non-limiting embodiment. The second sacrificial material 230 mayenter the vertical via 114 to form a sacrificial pillar 214. The process200 may further include etching the second sacrificial material 230using a first mask, to form an encasing member 216. The first mask maybe the only mask in the method according to various non-limitingembodiments that is in addition to the standard process of fabricatingthe MEMS device 110. In other words, the first mask may be the only maskin the method that is used solely for the purpose of packaging the MEMSdevice 110. The encasing member 216 may define a space that willsubsequently form an upper cavity of the MEMS device 110. The encasingmember 216 may also serve to support a cap structure that may besubsequently formed over the MEMS device 110. The encasing member 216,the sacrificial pillar 214, and the lower sacrificial member 106 mayform an integral sacrificial structure that may be removable in a singleetching step.

FIG. 3 illustrates a non-limiting process 300. The process 300 mayinclude depositing a layer of third sacrificial material 318 such thatthe active region 104 may be covered with the third sacrificial material318. The third sacrificial material 318 may include or consist of thesame material as the first sacrificial material 130 and/or the secondsacrificial material 230. The process 300 may result in forming spacerregion(s) 320, which extend laterally out of the encasing member 216,over the active region 104 of the device area. The third sacrificialmaterial 318 may also be deposited at least substantially verticallyabove the electrical contact points 112 a and 112 b.

FIG. 4 illustrates a non-limiting process 400. The process 400 mayinclude etching the layer of third sacrificial material 318 using asecond mask. The process 400 may remove the third sacrificial material318 at only one of the spacer region(s) 320, to form an indentation 420.The indentation 420 may expose the underlying active region 104. Theindentation 420 may serve to receive an anchor of a cap structuresubsequently. The process 400 may also remove part of the material ofthe active region 104, causing the active region 104 to recede. Theprocess 400 may also remove the third sacrificial material 318 above theupper electrical contact point 112 a, to form an upper contact via 422.The upper contact via 422 may expose the upper electrical contact point112 a. In other words, the indentation 420 and the upper contact via 422may be formed at the same time, in a single process, using the sameetching mask.

FIG. 5 illustrates a non-limiting process 500. The process 500 mayinclude etching the layer of third sacrificial material 318, togetherwith part of the wafer, using a third mask. The process 500 may form alower contact via 524 by removing the third sacrificial material 318 andpart of the active region 104 that lies at least substantiallyvertically above the lower electrical contact point 112 b. The lowercontact via 524 may expose the lower electrical contact point 112 b.

FIG. 6 illustrates a non-limiting process 600. The process 600 mayinclude depositing a metal layer 630 over the third sacrificial material318, as well as areas of the device wafer 140 and the electrical contactpoints 112 a, 112 b that are exposed. The metal layer 630 may be ahomogenous layer formed from a single metal, for example Al, Cu, orcombinations thereof, in a non-limiting embodiment. The metal layer 630may extend into the indentation 420, to form an anchor 620. The metallayer 630 may cover the other spacer region(s) 320 that does not have anindentation. The metal layer 630 may also at least substantially coatthe encasing member 216. The metal layer 630 may also extend into, andcoat the walls of each of the upper contact via 422 and the lowercontact via 524. The metal layer 630 may also coat the exposed surfacesof each of the upper electrical contact point 112 a and the lowerelectrical contact point 112 b.

FIG. 7 illustrates a non-limiting process 700. The process 700 mayinclude etching the metal layer 630 using a fourth mask. The process 700may include patterning the metal layer 630. After the patterning of themetal layer 630, the previously contiguous metal layer 630 is separatedinto several members, including a metal cap 732, an upper electricalcontact pad 734 and a lower electrical contact pad 736. The process 700may remove the metal layer 630 that lies above the spacer region(s) 320that does not have an indentation, so that the spacer region(s) 320 isexposed. The process 700 may also separate the metal layer 630 incontact with the upper electrical contact point 112 a from the metallayer 630 in contact with the lower electrical contact point 112 b. Themetal cap 732 may conform to the shape of the encasing member 216. Themetal cap 732 may at least partially envelope the encasing member 216.The metal cap 732 may be anchored to the device wafer 140 only at oneside, at the anchor 620. The metal cap 732 may be unanchored to thedevice wafer 140, above another spacer region(s) 320. The upperelectrical contact pad 734 and the lower electrical contact pad 736 maybe part of the redistribution layer (RDL) of the device wafer 140.

FIG. 8 illustrates a non-limiting process 800. The process 800 mayinclude removing the first sacrificial material 130, the secondsacrificial material 230 and the third sacrificial material 318 byetching in a non-limiting embodiment. The encasing member 216, thesacrificial pillar 214 and the lower sacrificial member 106 may bereleased through a gap 840 between the metal cap 732 and the devicewafer 140. The gap 840 may be laterally offset from the device area. Themetal cap 732 may include an extension member that forms a lateralchannel 950 with the device wafer 140, and the gap 840 may be an openingto the lateral channel 950. An upper cavity 816 may be formed betweenthe MEMS device 110 and the metal cap 732 after removal of the encasingmember 216. A lower cavity 806 may be formed between the MEMS device 110and the substrate 102 after removal of the lower sacrificial member 106.A vertical via 114 may be formed after removal of the sacrificial pillar214.

FIG. 9 illustrates a non-limiting process 900. The process 900 mayinclude depositing a sealing layer 940. The sealing layer 940 may sealthe gap 840, thereby encapsulating the MEMS device 110 under the metalcap 732. The sealing layer 940 may overlay the entire top surface of thedevice wafer 140, such that the metal cap 732, the anchor 620, the upperelectrical contact pad 734, the lower electrical contact pad 736, andexposed portions of the active region 104 are all coated with thesealing layer 940. The sealing layer 940 may also reach into the uppercontact via 422 and the lower contact via 524, to coat the walls of eachof these contact vias. The sealing layer 940 may also serve as apassivation layer. The sealing layer 940 may include a protectivematerial, such as an oxide or nitride, such as but not limited tosilicon dioxide, silicon nitride, or a combination thereof (e.g. asealing layer having a multi-layered combination). The sealing layer 940may include the same material as any one of the first sacrificialmaterial 130, the second sacrificial material 230, or the thirdsacrificial material 318.

FIG. 10 illustrates a non-limiting process 1000. The process 1000 mayinclude etching the sealing layer 940 using a fifth mask to open theelectrical contact pads, i.e. to expose the upper electrical contact pad734 and the lower electrical contact pad 736. The MEMS device 110 may beelectrically coupled to external devices or circuits through the upperelectrical contact pad 734 and the lower electrical contact pad 736.

FIG. 11 illustrates a simplified cross-sectional view of a MEMS package1100 according to various non-limiting embodiments. The MEMS package1100 may include the end product of the processes 100 to 1000. The MEMSpackage may include the device wafer 140, the metal cap 732, the sealinglayer 940, the upper electrical contact pad 734 and the lower electricalcontact pad 736. The MEMS package 1100 may further include an oxidelayer 1250 under the device wafer 140, and a further substrate 1260under the oxide layer 1250. The oxide layer 1250 may serve as aninsulator. The substrate 102 may include silicon such that the devicewafer 140 may be a silicon-on-insulator (SOI) wafer.

The device wafer 140 may include a MEMS device 110 in a device area. TheMEMS device 110 may include an active element 1110. The active element1110 may include the upper electrode 108 a and the lower electrode 108b. The active element 1110 may further include a transducer material,for example, a piezoelectric material, between the upper electrode 108 aand the lower electrode 108 b. The device area may include a lowercavity 806 under the active element 1110 and an upper cavity 816 abovethe active element 1110. The upper cavity 816 and the lower cavity 806may be connected through a vertical cavity, herein referred to as thevertical via 114. The MEMS device 110 may be partially encapsulated by ametal cap 732. The metal cap 732 may be partially anchored to the devicewafer 140. The metal cap 732 may include an anchored portion, i.e. apart of the metal cap 732 that is anchored to the device wafer 140, aswell as an unanchored portion, i.e. a part of the metal cap 732 that isnot anchored to the device wafer 140. The metal cap 732 may include afirst extension member 1120 that includes an anchor 620. The firstextension member 1120 may extend laterally away from the MEMS device 110in a first direction, and extend towards the device wafer 140. Theportion of the first extension member 1120 that extends towards thedevice wafer 140 may be referred to as an anchor 620. The firstextension member 1120 may be secured to the device wafer 140 at theanchor 620. The anchor 620 may be partially embedded into the devicewafer 140, at the active region 104. The metal cap 732 may include asecond extension member 1122. The second extension member 1122 mayextend laterally away from the MEMS device 110 in a direction differentfrom the first direction. The second extension member 1122 may hangabove the device wafer 140 such that a gap 840 exists between the secondextension member 1122 and the device wafer 140. The gap 840 may serve asa release via for removing sacrificial material that defined the areasfor the lower cavity 806, the upper cavity 816, and the vertical via114. The gap 840 may be laterally offset relative to the MEMS device110. In other words, the gap 840 may not be positioned directly abovethe MEMS device 110. The gap 840 may be a side opening that leads to theupper cavity 816. The second extension member 1122 may define a lateralchannel with respect to the device wafer 140. A first end of the lateralchannel opens to the upper cavity 816, while a second end of the lateralchannel is closed up by the sealing layer 940 which is uniformly spreadacross the entire top surface of the device wafer 140 and over the metalcap 732. The sealing layer 940 may have the same thickness across thedevice wafer 140. The sealing layer 940 may be the topmost layer of theMEMS package 1100, thereby sealing and passivating the device wafer 140.The second end, which is also referred herein as the gap 840, may opposethe first end of the lateral channel. As the release via is a lateralchannel, the area of the device wafer 140 available for the MEMS device110 may be maximized, unlike a vertical release via where the area ofthe device wafer 140 directly underneath the vertical release via may beunusable space. As such, the footprint of the MEMS package may bereduced.

The metal cap 732, together with the sealing layer 940, may fullyencapsulate the MEMS device 110, including both the upper cavity 816 andthe lower cavity 806. The overall thickness of the MEMS package 1100 maybe less than 200 um, for example in a range of 100 um to 150 um, whichis substantially thinner than MEMS packages fabricated by wafer-levelcapping. The slim form factor of the MEMS package 1100 may be achievableas the encapsulation layers consisting of the metal cap 732 and thesealing layer 940 are thinner than a cap wafer. Also, the metal cap 732may shield the MEMS device 110 from EM interferences and as such, it isunnecessary to include a separate EM shielding structure within the MEMSpackage 1100, further reducing the thickness of the MEMS package 1100.The metal cap 732 also lies within the same layer as the RDL by virtueof being formed in the same process step. The metal cap 732, the upperelectrical contact pad 734 and the lower electrical contact pad 736 maybe identical in composition, as well as thickness, by virtue of beingformed from the same metal layer 630, in the same process step.

FIG. 12A illustrates a partial cross-sectional view 1200A of the MEMSpackage 1100. The line AA′ indicates a cut across the MEMS package 1100.

FIG. 12B illustrates a partial top view 1200B of the metal cap 732, whenthe MEMS package 1100 is cut across the line AA′ shown in FIG. 12A. Thepartial top view 1200B shows only the device area of the MEMS package1100. The metal cap 732 may be anchored to the device wafer 140 alongpart of a periphery of the device area. In other words, the anchor 620of the metal cap 732 may form a partial perimeter around the MEMS device110. The metal cap 732 may be unanchored to the device wafer 140 at anunanchored region, also referred herein as the lateral channel 950. Thelateral channel 950 may include two open ends, one leading to the uppercavity 816 and the open end leading to the gap 840 which is sealed bythe sealing layer 940.

According to various non-limiting embodiments, a MEMS package mayinclude a wafer, a metal cap, an electrical contact pad and a sealinglayer. The wafer may include a MEMS device. The metal cap may be atleast partially anchored to the wafer where at least one point betweenthe cap and the wafer may be unanchored. The metal cap may at leastsubstantially extend over the MEMS device. The electrical contact padmay be electrically coupled to the MEMS device. The sealing layer may bedisposed over the metal cap and the wafer. The sealing layer may beuniform in thickness of the metal cap and the wafer. The sealing layermay seal a gap between an unanchored portion of the metal cap and thewafer, to encapsulate the MEMS device. The MEMS package may include anupper cavity between the metal cap and the MEMS device. The MEMS packagemay include a lower cavity at a lower surface of the MEMS device. Thelower surface may oppose an upper surface of the MEMS device. The uppersurface may face the metal cap. The upper surface of the MEMS device mayhave an indentation. The metal cap may be anchored to the wafer at theindentation. The unanchored portion of the metal cap may extend beyondthe MEMS device. The electrical contact pad and the metal cap mayinclude the same composition, and may also have the same thickness.

In other words, according to various non-limiting embodiments, a MEMSpackage may include, or may be the MEMS package 1100. The MEMS packagemay include a wafer, a metal cap, an electrical contact pad and asealing layer. The wafer may include, or may be the device wafer 140.The metal cap may include, or may be the metal cap 732. The electricalcontact pad may include, or may be, the upper electrical contact pad 734and/or the lower electrical contact pad 736. The sealing layer mayinclude, or may be, the sealing layer 940. The metal cap may at leastsubstantially overhang the MEMS device, so as to shield the MEMS devicefrom EM waves. The metal cap may also provide structural strength to thethin film encapsulation of the MEMS device. The thin film encapsulationmay include the metal cap and the sealing layer. The metal cap may notfully encapsulate the MEMS device, as a release via may be required, torelease sacrificial material in order to form cavities within the MEMSdevice. The sealing layer may overlay the metal cap and may be fullyanchored to the wafer, so as to hermetically seal the MEMS device andthe cavities. The cavities may include an upper cavity above a moveableelement of the MEMS device and a lower cavity below the moveableelement. The electrical contact pad(s) may be part of a RDL. Theelectrical contact pad(s) may be formed in the same layer as the metalcap, such that the electrical contact pad(s) and the metal cap may beidentical in composition, and possibly identical in thickness.

FIG. 13 illustrates a flow diagram 1300 of a method for packaging a MEMSdevice according to various non-limiting embodiments. The MEMS devicemay be, for example, the MEMS device 110. The method may includeproviding a metal cap that is partially anchored to a wafer thatincludes the MEMS device. At least one point between the cap and thewafer may be unanchored. The metal cap may be the metal cap 732. Thewafer may be the device wafer 140. The metal cap may be arranged to atleast substantially extend over the MEMS device. Element 1302 mayinclude providing a sacrificial structure on the wafer. Providing thesacrificial structure may include depositing a first layer ofsacrificial material over the wafer and etching the first layer ofsacrificial material to form an encasing member, which may includeprocess 200. Providing the sacrificial structure may further includedepositing a second layer of sacrificial material to form a spacerregion(s), which may include process 300. Providing the sacrificialstructure may further include etching the second layer of sacrificialmaterial to expose the wafer at one side of the MEMS device, which mayinclude process 400. The metal cap may be anchored to the wafer at theone side of the MEMS device where the wafer is exposed. The process 400may also expose an electrical contact pad that is electrically coupledto the MEMS device. The sacrificial structure may include the encasingmember to encase the MEMS device. The sacrificial structure may includethe spacer region(s) recessed relative to the encasing member. Thespacer region(s) may extend out of the encasing member. The spacerregion(s) may be laterally offset from the MEMS device. The encasingmember may be the encasing member 216. The spacer region(s) may be thespacer region(s) 320. Element 1302 may further include depositing ametal layer over the sacrificial structure and the wafer, and etchingthe metal layer using a single etch mask to form the metal cap, anelectrical contact pad and an opening over the spacer region(s). Inother words, the element 1302 may include process 600. The metal layermay be the metal layer 600. The electrical contact pad may include theupper electrical contact 734 and/or the lower electrical contact 736.The method may further include forming an upper cavity between the metalcap and the MEMS device by releasing the sacrificial material throughthe opening, which may include process 800. The upper cavity may be theupper cavity 816. The method may further include providing a furthersacrificial material between the MEMS device and a substrate of thewafer. The further sacrificial material may be the first sacrificialmaterial 130 of the lower sacrificial member 106. The method may furtherinclude releasing the further sacrificial material through the openingto form a lower cavity between the MEMS device and the substrate. Thelower cavity may be the lower cavity 806.

The method may further include electrically coupling an electricalcontact pad to the MEMS device. Element 1304 may include process 600.The electrical contact pad may include the upper electrical contact pad734 and/or the lower electrical contact pad 736. The method may furtherinclude providing a sealing layer over the metal cap and the wafer suchthat the sealing layer seals a gap between an unanchored portion of themetal cap and the wafer to encapsulate the MEMS device. The sealinglayer may be the sealing layer 940. Element 1306 may include process900. Element 1306 may include depositing a passivation material over themetal cap, the wafer and the electrical contact pad. Element 1306 mayalso include etching the passivation material to expose the electricalcontact pad, which may include process 1000. The unanchored portion ofthe metal cap may be at least partially formed over the spacerregion(s). The electrical contact pad and the metal cap may include thesame composition. The method may include forming the electrical contactpad and the metal cap in the same metal layer and as such, theelectrical contact pad and the metal cap may also have the samethickness.

The following examples pertain to further embodiments.

Example 1 is a MEMS package including a wafer having a MEMS device; ametal cap partially anchored to the wafer where at least one pointbetween the cap and the wafer is unanchored, the metal cap at leastsubstantially extending over the MEMS device; an electrical contact padelectrically coupled to the MEMS device; and a sealing layer disposedover the metal cap and the wafer, such that the sealing layer seals agap between an unanchored portion of the metal cap and the wafer toencapsulate the MEMS device; wherein the electrical contact pad and themetal cap include the same composition.

In example 2, the subject-matter of example 1 can optionally includethat the unanchored portion of the metal cap extends beyond the MEMSdevice.

In example 3, the subject-matter of example 1 or example 2 canoptionally include that the MEMS package includes an upper cavitybetween the metal cap and the MEMS device.

In example 4, the subject-matter of any one of examples 1 to 3 canoptionally include that the MEMS package includes a lower cavity at alower surface of the MEMS device, the lower surface opposing an uppersurface of the MEMS device facing the metal cap.

In example 5, the subject-matter of any one of examples 1 to 4 canoptionally include that an upper surface of the MEMS device facing themetal cap has an indentation, wherein the metal cap is anchored to thewafer at the indentation.

In example 6, the subject-matter of any one of examples 1 to 5 canoptionally include that the electrical contact pad and the metal cap areidentical in thickness.

Example 7 is a method for packaging a MEMS device. The method mayinclude providing a metal cap that is partially anchored to a waferincluding the MEMS device where at least one point between the cap andthe wafer is unanchored, the metal cap arranged to at leastsubstantially extend over the MEMS device; electrically coupling anelectrical contact pad to the MEMS device; and providing a sealing layerover the metal cap and the wafer such that the sealing layer seals a gapbetween an unanchored portion of the metal cap and the wafer toencapsulate the MEMS device; wherein the electrical contact pad and themetal cap include the same composition.

In example 8, the subject-matter of example 7 can optionally includethat providing the metal cap includes: providing a sacrificial structureon the wafer, the sacrificial structure including an encasing member toencase the MEMS device and one or more spacer regions recessed relativeto the encasing member, wherein the one or more spacer regions extendout of the encasing member; depositing a metal layer over thesacrificial structure and the wafer; and etching the metal layer using asingle etch mask, to form the metal cap, the electrical contact pad, andan opening over the one or more spacer regions.

In example 9, the subject-matter of example 8 can optionally includethat the spacer region is laterally offset from the MEMS device.

In example 10, the subject-matter of example 8 or example 9 canoptionally include that providing the sacrificial structure includes:depositing a first layer of sacrificial material over the wafer; etchingthe first layer of sacrificial material to form the encasing member;depositing a second layer of sacrificial material to form the one ormore spacer regions; and etching the second layer of sacrificialmaterial to expose the wafer at one side of the MEMS device.

In example 11, the subject-matter of example 10 can optionally includethat etching the second layer of sacrificial material also exposes oneor more electrical contact points of the MEMS device.

In example 12, the subject-matter of example 10 or example 11 canoptionally include that the metal cap is anchored to the wafer at theone side of the MEMS device where the wafer is exposed.

In example 13, the subject-matter of any one of examples 8 to 12 canoptionally include that the unanchored portion of the metal cap is atleast partially formed over the one or more spacer regions.

In example 14, the subject-matter of any one of examples 8 to 13 canoptionally include: forming an upper cavity between the metal cap andthe MEMS device by releasing the sacrificial material through theopening.

In example 15, the subject-matter of any one of examples 8 to 14 canoptionally include: providing a further sacrificial material between theMEMS device and a substrate of the wafer; and forming a lower cavitybetween the MEMS device and the substrate by releasing the furthersacrificial material through the opening.

In example 16, the subject-matter of any one of examples 7 to 15 canoptionally include that providing the sealing layer includes: depositinga passivation material over the metal cap, the wafer, and the electricalcontact pad; and etching the passivation material to expose theelectrical contact pad.

In example 17, the subject-matter of any one of examples 7 to 16 canoptionally include that the electrical contact pad and the metal cap areidentical in thickness.

While embodiments of the invention have been particularly shown anddescribed with reference to specific embodiments, it should beunderstood by those skilled in the art that various changes in form anddetail may be made therein without departing from the spirit and scopeof the invention as defined by the appended claims. The scope of theinvention is thus indicated by the appended claims and all changes whichcome within the meaning and range of equivalency of the claims aretherefore intended to be embraced. It will be appreciated that commonnumerals, used in the relevant drawings, refer to components that servea similar or the same purpose.

It will be appreciated to a person skilled in the art that theterminology used herein is for the purpose of describing variousembodiments only and is not intended to be limiting of the presentinvention. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

It is understood that the specific order or hierarchy of blocks in theprocesses/flowcharts disclosed is an illustration of exemplaryapproaches. Based upon design preferences, it is understood that thespecific order or hierarchy of blocks in the processes/flowcharts may berearranged. Further, some blocks may be combined or omitted. Theaccompanying method claims present elements of the various blocks in asample order, and are not meant to be limited to the specific order orhierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” The word “exemplary” is used hereinto mean “serving as an example, instance, or illustration.” Any aspectdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects. Unless specifically statedotherwise, the term “some” refers to one or more. Combinations such as“at least one of A, B, or C,” “one or more of A, B, or C,” “at least oneof A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or anycombination thereof” include any combination of A, B, and/or C, and mayinclude multiples of A, multiples of B, or multiples of C. Specifically,combinations such as “at least one of A, B, or C,” “one or more of A, B,or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and“A, B, C, or any combination thereof” may be A only, B only, C only, Aand B, A and C, B and C, or A and B and C, where any such combinationsmay contain one or more member or members of A, B, or C. All structuraland functional equivalents to the elements of the various aspectsdescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. The words “module,” “mechanism,” “element,” “device,” andthe like may not be a substitute for the word “means.” As such, no claimelement is to be construed as a means plus function unless the elementis expressly recited using the phrase “means for.”

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A method for packaging a MEMS device, the methodcomprising: providing a metal cap that is partially anchored to a wafercomprising the MEMS device where at least one point between the cap andthe wafer is unanchored, the metal cap arranged to at leastsubstantially extend over the MEMS device; electrically coupling anelectrical contact pad to the MEMS device; and providing a sealing layerover the metal cap and the wafer such that the sealing layer seals a gapbetween an unanchored portion of the metal cap and the wafer toencapsulate the MEMS device; wherein the electrical contact pad and themetal cap comprise the same composition.
 2. The method of claim 1,wherein providing the metal cap comprises: providing a sacrificialstructure on the wafer, the sacrificial structure comprising an encasingmember to encase the MEMS device and one or more spacer regions recessedrelative to the encasing member, wherein the one or more spacer regionsextend out of the encasing member; depositing a metal layer over thesacrificial structure and the wafer; and etching the metal layer using asingle etch mask, to form the metal cap, the electrical contact pad, andan opening over the one or more spacer regions.
 3. The method of claim2, wherein the spacer region is laterally offset from the MEMS device.4. The method of claim 2, wherein providing the sacrificial structurecomprises: depositing a first layer of sacrificial material over thewafer; etching the first layer of sacrificial material to form theencasing member; depositing a second layer of sacrificial material toform the one or more spacer regions; and etching the second layer ofsacrificial material to expose the wafer at one side of the MEMS device.5. The method of claim 4, wherein etching the second layer ofsacrificial material also exposes one or more electrical contact pointsof the MEMS device.
 6. The method of claim 4, wherein the metal cap isanchored to the wafer at the one side of the MEMS device where the waferis exposed.
 7. The method of claim 2, wherein the unanchored portion ofthe metal cap is at least partially formed over the one or more spacerregions.
 8. The method of claim 2, further comprising: forming an uppercavity between the metal cap and the MEMS device by releasing thesacrificial material through the opening.
 9. The method of claim 2,further comprising: providing a further sacrificial material between theMEMS device and a substrate of the wafer; and forming a lower cavitybetween the MEMS device and the substrate by releasing the furthersacrificial material through the opening.
 10. The method of claim 1,wherein providing the sealing layer comprises: depositing a passivationmaterial over the metal cap, the wafer, and the electrical contact pad;and etching the passivation material to expose the electrical contactpad.
 11. The method of claim 1, wherein the electrical contact pad andthe metal cap are identical in thickness.